Method of and apparatus for hardening manganese-steel articles



F. SCHAFFER.

METHOD OF AND APPARATUS FOR HARDENING MANGANESE STEEL ARTICLES.

APPLICATION FILED JAN. 23, I9IT.

Patented Dec. 14, 1920.

I ay 1 UNITED STATES- PATENT OJFFICE.

FRIEDRICH SCI-IAFFER, or LEOIBERSDORF, NEAR VIENNA, AUSTRIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO T E CHEMICAL EoUNnArIoN, INc., A CORPORATION or DELAWARE METHOD OF AND APPARATUS FOR- HARDENrING MANGANESE-STEEL ARTICLES.

Specification of Letters Patent. Patented D 14 1920 Applicaiton filed January 23, 1917. Serial No. 143,943.

To all whom it may (3mm: v Be it known that 1,,FRIEDRICH j SCHAFFER,

' it works manager, a subject of theigEm'peror of Austria, andres iden t' of Leobersdorf,

near Vienna, in the Empire of Austria, have... invented certain new and usefu-l' -Improve ments in Methods of and Ap aratus for I Hardening Manganese Steel rticles, of which the following is a specification.

My invention relates to a method of and apparatus for the heat treatment of manganese steel articles, in particular such having an intricate shape, whereby these latter are enabled to undergo the heat treatment without the liability of any stress occurring in the material in the course of the consecutive series of operations to which the piece is subjected. v

A further object of my invention is to render it possible to so select the structure of the steel employed, that it will consist through-- out of either pure austenite, or austenite and free carblds, or else, of austenite with a larger proportion of free carbi-ds-the structure being everywhere the sameso that, in consequence, the smallest hardness and a maximum of elongation, or a greater hardness and a smaller elongation may be obtained in entire accordance with the purpose to which the piece is intended to be applied.

astly, according to my invention, the heat treatment of the said articles may be eflected by automatic means, it being obvious that if a large number of pieces of the same size and shape are to be treated, they must be equal in structure, in their mechanical properties and show no stresses.

The common known manganese steel, containing about one per cent. of carbon and twelve per cent. ofmanganese, will possess the best mechanical properties after havin been subjected to a proper heat treatment? This last, as known, consists in heating the piece up to about 100 to 1100 C. and then quenching it in water or oil.

Where the material in the piece is not uniformly distributed, so that different cross sections, that is to say, large and small, will happen to be side by side; in which event the cooling surface of the large sections (where the material has amassed) is relatively smaller than the cooling surface of the small sections (possessing less material),

then it will be obvious that during the quenching operation the cooling down of the material will be quicker or sloweriin the different partsof the piece. Now these differences in the rapidity of the cooling give rise to the formation of stresses which are liable to seriously injure the piece and possibly render it absolutely useless.

In the event of the manganese steel containmg about one per cent. of carbon, while the proportion of manganese proper is raised, then, in accordance with my invention, for the customary quenching operation may be substituted a slower cooling operation, and one which will insure the obtaining of the very same excellent mechanical properties that would be obtained if a steel of the kind mentioned, having about twelve percent. of manganese where quenched.

Thus, for instance, a steel containing about one per cent. of carbon and more than seventeen per cent. of manganese, may be subjected to the following treatment:

The piece is first heated up to from 1000 to 1100 C. and then gradually allowed to cool down in intervals of from two to three minutes duration, at first to 700, then down to 500, then to 420, then to 370, then to 320, then to 280, then to 240, then to 200, and so on; the entire operation of cooling the piece from 1050 down to 200 C. having required about twenty-four minutes. Or, as another example: A steel containing about one per cent. of carbon and about sixteen per cent. of manganese is to be cooled down in a manner similar to the aforesaid steel, and this according to the following datas: In intervals of two minutes from 1050 C. to 700 (1, then to 500 C., then to 460 C., then to 380 0., then to 350 0., then to 320 0., then to 260 0., then to 240 C., then to 180 (3., and so forth; the entire operation of cooling the piece from 1050 C.

further correct any faults in the cooling which may arise through any possible inaccurate distribution of the cooling media, as will be described hereinafter. In any case, however, the drop in temperature will be uniform all over the piece, so that no stresses whatever can arise, and the structure will remain the same throughout the whole piece. By cooling the piece in accordance with 0 the above-indicated curve of time and temperature as therein given by way of example, the entire body of the piece will show pure austenitev throughout the structure. Carrying out the cooling operation more rapidly will not affect the structure of the piece, it will still remain pure austenite; carrying it out more slowly, will on the other hand, change the structure, so that the latter will show austenite in combination with free carbids. In this latter event, the piece will be harder and its elongation will be less than what it would be in the case of pure austenite.

It consequently follows that the slower the cooling operation, the more free carbids will be obtained; the hardness of the piece will increase, and the elongation of the material will diminish.

This property peculiar to steel having one per cent. of carbon and more than twelve per cent. of manganese, renders it possible to employ the heat treatment in connection with pieces, the material of which is unevenly distributed, without any liability of stresses occurring. The said property in addition, affords the possibility of making 'use v of automatic devices in connection with the coolin operation; which devices will be described by way of example at length hereinsame size and shape, an equality of structure and of mechanical properties will be secured. The said property finally admits of so selectingthe structure that the piece may be made harder with a reduced elongation, or it may be made softer with a higher degree of elongation, in full accordance with the purpose for which the piece is to be employed.

In the accompanying drawing there is shown by way of example an embodiment of the apparatus intended to carry out the process according to my invention, in which igure 1 illustrates a top view with a barred window in place, and in Fig. 2 a cross section, whereas Fig. 3 is a diagrammatic view of the electrical device intended to operate the said apparatus:

As will be seen from the drawing, the frame of the barred window, chosen by way 4 of example, possesses a much larger cross section than do the bars. Now in the event' of a barred window of this kind, made of manganese steel containing about twelve per cent. of manganese, being toughened according to the method hitherto in use, what is after, so that in v,the making of pieces of the.

cooling operation done, is to heat the window up to a temperature of from. 1000 to 1100 -C. and then quenching it in water or in oil, thus causing the bars to shrink much quicker than as aframe portion, the result of which, the bars will burst. In accordance with my invention, the barred window is made of steel containlng about; one per cent. of carbon and more than seventeen per cent. of manganese and the cooling operation is effected in ac 5 cordance with the data of the curve of time and temperature above mentioned. The entire cooling operation is carried out in a series of stages. Each stage comprises the action of cooling the piece in asuitable bath until a predetermined temperature ha been attained, and then allowing the piece to remain in the open air for about two to three minutes whereby an equalization of temperature is obtained throughout the mass. Thus the cooling and equalizing operations alternate, until the entire piece has sufliciently cooled down. In a number of similar pieces, say, for example, barred windows,'of the same size and shape are to be toughened in succession, then the automatic device illustrated in the drawing is made use of. I

In Figs. 1. and 2, the cases 2, 3 and 2 are adapted for containing and guiding the coolin medium. Each of the said cases is provi ed with nozzles for the delivery of the coolin medium; Case 3 is hin ed on to case 2 1n a way, such as will ena le the coolin medium to fiow from case 2 to case 3. -W ith case 3 turned up at 4, the piece, which has meanwhile been 'heated up properly, is inserted in case 2, whereupon case 3 shuts down and the cooling operation is ready to begin. The nozzles vary in size according to the area of the cross sections intended to be cooled. Thus, as shown in Fig. 2 the nozzles arranged to cool the frame section of the barred window are larger in size than those adapted for cooling the bar sections. The size of the nozzles employed is so chosen, that the amount of heat to be absorbed from the bigger parts of the window is proportionately greater than that absorbed from the smaller parts thereof; In this manner, there is just so much heat absorbed along every point of the entire piece, that the drop in temperature will be uniform in every section thereof. It will be obvious that in thecooling of pieces of an intricate shape, the proportionate amount of heat absorbed cannot be quite accurate so that the drop in temperature will consequently not be absolutely equal at every point and stresses are bound to arise. To eliminate this particular drawback, the

according to my invention, and as already hereinbefore set forth, is divided into a series of steps or stages, each of which consists in alternately cooling and then resting the piece for a cerand 3 are connected to valve 5 while case.

2 is in communication with valve 6% The sa d valves are governed say, for example, by an electrical device such as is shown d1a-.

grammatically in Fig. 3, in which 7 indicates an electric generator, 9 a revolving drum having contact pieces 10, adapted for switching on and off the electric current on the magnet 8. This latter serves to correspondingly open and shut the valve 5 or iihe valve 6 which latter is not shown'in By aid of this arrangement, the suitable amount of cooling medium may be supplied to the variously dimensioned nozzles when-- soever desired. By timing the revolving speed of the drum 9 and by suitably dimensioning the contact pieces 10, the entire cooling of the piece, in the present instance, a barred window, may be carried out within and along a certain curve of time and temperature, as hereinbefore set forth by way of illustration. The result of the treatment according to my invention is that the piece will possess at its every part, the pure austenitic structuge. By altering both the velocity of the drum 9 and the dimensions of the contact pieces 10, the cooling operation may 1 be either shortened or prolonged. As has already been stated, cooling the piece more quickly, will be productive of a pure austenltic structure; cooling the piece less quickly will result in the production of pure austen-- And the-slower they ite and free carbids. cooling, the more of free carbids will be obtained, theharder the piece will become, and the less will be the elongation. The mechanical properties of the steel may be selected, according to the purpose to which the piece is to be applied, anywhere from the slightest to the utmost degree of hardness, as also from a maximum to a minimum of elongation which this particular material will admit of. Y

I wish it to be. distinctly understood that the piece (barred'window) and'the device ;mentioned in the foregoing description are -only taken by way of illustration, and that, in point of .fact, and forall general purposes, the piece to be subjected to the cooling operation may be of-any shape and character desired, as also that the automatic device may be constructed in many other ways without departing from the spirit of my invention, andthat the method of cooling, which is specially characterized by the curve of time and temperature, may be chosen in any other manner suitable and likel to insure the. mechanical properties which it is desired shall be obtained.

The automatic device is to be constructed in the following manner: I

' The sizes of the parts of the device adapted for guiding the'cooling medium, parts such as the valves, -cases, nozzles, and the like, should be so proportioned as to be in strict accordance with the amount of heat stored up and the. extent of cooling surface area available in the several individual sections of the piece, in such a manner as to insure the drop in temperature to be one and the same all over the piece. Because of the fact that this requirement cannot be strictly complied with in most cases, as some pieces will be of a most intricate shape, and with the material throughout unevenly distributed it is necessary, according to my inven: tion, that the cooling operation shall be carried out not in one continuous operation, but in a series of steps or stages, each stage comprising cooling the piece in a suitable bath and then allowing to remain for about two to three minutes in the open air in order to equalize any differences in temperature that may exist in the various parts of the piece intended to be employed. By working in accordance with the indications hereinbefore given, the desired structure will be uniformly obtained at every point of the piece.

What I claim is l. The method of hardening objects of varying cross-sections made of manganese steel containing about 1% carbon and more than 12% manganese, which method consists .in heating the object to be treated to from 1000 C. to 1100 C. and then successively cooling it in stages of certain definite time intervals gradually down to the final temperature, the cooling medium employed on the various parts of the object under treatment being proportioned in accordance with the varying cross-sections of the said object.

2. The method as set forth in claim 1, further specified in that the entire cooling operation is divided into successive stages separated by certain definite time intervals, each stage comprising a cooling operation followed by a period of rest sufiicient to allow for equalization of any differences of tem perature existing in the various parts of the object under treatment.

3. An apparatus for hardening manganese steel articles comprising containers for a liquid cooling medium, nozzles of various sizes connecting therewith for applying said liquid cooling medium simultaneously to all parts of-the object under the treatment and so constructed as to apply the liquid cooling medium in proper proportion to the varying cross-sections of the different parts of said object, and valves for controlling the flow of the cooling medium thus applied.

4. An apparatus for hardening manganese steel articles comprising containers for a liquid cooling medium, nozzles of various sizes connectingjherewith for applying said liquid cooling medium simultaneousl to all parts of the object under the treatment and so constructed as to apply the liquid cooling medium in proper proportion to the varying cross-sections of the difi'erent parts of said object, and valves 'for controlling the flow of the cooling medium thus applied sai'cl valves being arranged with electrical controls whereby the flow of the cooling medium is automatically interrupted.

Signed by me at Vienna, in the Empire of Austria, this 3rd da of November, 1916.

FRIEDR SOHAFFER. Witnesses:

ARTHUR LINDENSTEAD, JOHANN FLEISCHMANN. 

